1. Field of the Invention
The present invention relates to a laser ignition system having at least one means for producing a pulsed laser beam and at least one means for focusing the produced pulsed laser beam onto a focal zone, for example in order to ignite a combustible gas mixture in an internal combustion engine or burner.
2. Description of the Related Art
In current laser applications for laser ignition, a main focus of attention is achieving the smallest possible focusability of the laser light. Through the use of optical equipment having a large numerical aperture (DIN 58629-1), the goal is pursued of achieving the smallest possible beam diameter with the greatest possible intensity (power per surface=power density) in the focal zone. Koga et al. (Journal of Physics D 43 (2010), 025204) showed that, in addition to a threshold intensity, a minimum energy or minimum fluence (energy per surface=energy density) in the focal point is necessary for the ignition of a plasma.
However, it has turned out that despite high realized intensities, in particular given lean mixtures disadvantageous effects occur in laser ignition, such as misfires, which could result in engine failure. Associated with this is a lack of smooth running of the engine. The resulting increase in emission of pollutants has a negative influence on the competitiveness of laser ignition systems compared to conventional electrical ignition systems.